startFun();
			var i=0;
		function startFun(){
			window.setInterval("all()",2000);
		}
			
			
			function all(){
				i++;
				if(i%5==1){
					change1();
				}else if(i%5==2){
					change2();
				}else if(i%5==3){
					change3();
				}else if(i%5==4){
					change4();
				}
			}

		function change1(){
	
			document.getElementById("xx").style.backgroundImage="url(./img/lunbo/1920-1080.jpg)";
			 colorRes();
			document.getElementById("btn1").style.backgroundColor="#D3D4D3";
		}
		function change2(){
			document.getElementById("xx").style.backgroundImage="url(./img/lunbo/22b5340f6803292f2234ca71f5ff7de0.jpeg)";
			 colorRes();
			document.getElementById("btn2").style.backgroundColor="#D3D4D3";
		}
		function change3(){
			document.getElementById("xx").style.backgroundImage="url(./img/lunbo/yoona1.jpg)";
			 colorRes();
			document.getElementById("btn3").style.backgroundColor="#D3D4D3";
		}
		function change4(){
			document.getElementById("xx").style.backgroundImage="url(./img/lunbo/ChMkJ1bKx-aIYl2jAAPFZ_PRn64AALH6QKZSxMAA8V_254.jpg)";
			 colorRes();
			document.getElementById("btn4").style.backgroundColor="#D3D4D3";
		}
		function colorRes(){
			document.getElementById("btn1").style.backgroundColor="white";
			document.getElementById("btn2").style.backgroundColor="white";
			document.getElementById("btn3").style.backgroundColor="white";
			document.getElementById("btn4").style.backgroundColor="white";
		}
		
		window.alert("请确认您已经年满18！！");